The invention relates to a gas bag for a vehicle occupant restraint system comprising an inflation port and a wall. Such gas bags are inflated, when the vehicle is involved in a collision, within a few milliseconds by the gas provided by an inflator and serve to absorb the impact of the vehicle occupant.
It is often a disadvantage with conventional gas bags that they are inadequately adapted to the inflator output. The amount of gas expelled may vary greatly which in extreme situations may result in the gas bag being insufficiently filled or caused to rupture. In addition, such gas bags are typically dimensioned merely for vehicle occupants of average stature and weight. Thus, for example, as compared to the impact of a lightweight occupant, the typical gas bag does not offer additional possibilities for compensating the kinetic energy of a relatively heavy occupant to diminish the rebound of the heavy occupant from the gas bag.
From DE-A-20 30 863 there is known a gas bag comprising an inflation port and a wall, in which gas bag the wall comprises portions distributed across its surface area which, with increasing gas bag internal pressure, increase the volume of the gas bag by a deployment or smoothing action.
WO-A-9009295 discloses a gas bag in which tethers, made of stronger threads as compared with the remaining gas bag fabric, are interwoven with the gas bag wall at predetermined sites. As the fabric of the gas bag wall is pre-shrinked in contrast to the threads of the tethers, a controlled expanding of the gas bag can be achieved with the tethers.
The invention provides a gas bag which better adapts to the load concerned. By individually setting the volume and thus the hardness of the gas bag corresponding to the load, the gas bag may adapt to various crash situations as well as to various power outputs of the gas generator.
For this purpose it is made provision according to a first aspect of the invention that in a generic gas bag, as is known from the cited DE-A-20 30 863, the wall comprises folds formed by constrictions of the wall portions.
According to a second aspect of the invention the portions of the wall consist of a textile fabric comprising tear threads with loops woven therein.
According to a third embodiment the portions of the wall consist of a corrugated material.
The design of the gas bag in accordance with the invention results in the advantage that the risk of the gas bag rupturing at extremely high temperaturesxe2x80x94and the associated greater expansion of the gas generated by the inflator for inflating the gas bagxe2x80x94is reduced by the possibility of compensating the overpressure by providing an additional volume. As a result of this, the gas bag volume can be diminished so that the gas bag is adequately filled even at extremely low temperatures to offer the occupant protection.